Treatment of hydrocarbon oils



swept.2,1936v V fR. BDAY 2,055,027

TREATMENT oF HYDRocARBoN OILS Filed'oct. 3, 1932 Sheets-'sheet 1 Furzace fifa/17:95,

Sept. 22, 1936. y l R. B. DAY 2,055,027

TREATMENT OF' HYDROC'ARBON OILS Y Filed OC.. 5, 1952 3 Sheets-Sheet 2 sept. 22, 1936.

Las, oF 57% Aqueous ncl. PER BBL. oF GAsLlNE l R. B. DAY "2,055,027 y TREATMENT OF .HYDRKOCVARBON OILS Filed oor. 3, 1952` s sheets-sheet s HYDROCHLORIC ACID REQUIRED FOR TREATMENT 10o zoo soo 40o soo soo 'foo` GAUGEl PREssuRE,LBS.-PER SQUARE INCH.

Patented Sept. 22, 1936 UNITED STATES PATENT 'OFFICE TREATMENT or mmaocARON oILs Roland B. Day, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware This invention relates to the treatment of hydrocarbon oils and refers more particularly to the treatment of hydrocarbon oil distillates of motor` fuel boiling range produced by the cracking of 5 heavier and less valuable portions of petroleum oils though similar motor fuel fractions produced from other sources may also be treated such as those produced in the straighttrun distillation of crude petroleums or in the cracking of tars prolO duced in the primary distillation of coals, shales,

etc.

In a more specific sense the invention is concerned with a process which may be employed to controllably eliminate the undesirable constitl5 uents of primary or untreated motor fuel distillates, such constituents being classified generally as the gum-forming and colored compounds and the sulfur-containing derivatives, the latter imparting a bad odor to the distillates, and being zo 'corrosive upon the metal parts of automobile engines either before or after combustion.

The most generally used refining method for producing a refined and stable gasoline from primary naphthas consists in regulated treatment l5 of the same with concentrated sulfuric acid, followed by neutralization (with sweetenlng if necessary) and redistillation to produce refined gasoline as an overhead product. The disadvantages of this method lie generally in the cost of re- B agents and particularly in the high losses suffered in accomplishing the desired degree of refining. The present invention is a departure from the older method and possesses new and useful features which further differentiate it from 35 previous attempts to overcome the difficulties encountered in producing a stable refined gasoline from the raw naphthas produced in cracking operations with minimum losses. Other features and advantages will become evident in the development of the specification.

In one specific embodiment the invention comprises the treatment of hydrocarbon yoil distillates, particularly cracked hydrocarbon oil distillates of approximate motor fuel boiling range at elevated temperatures and under pressures sufficient to substantially prevent vaporization of said distillates with hydrochloric acid and zinc chloride.

A number of metal chlorides have been proposed at different times for the treatment of petroleum distillates such as cracked distillates to improve their properties. Among these chlorides may be mentioned those of zinc, tin, iron, aluminum, etc. According to the present invention the use of zinc chloride is preferable over these other chlorides on account of the superior treating effects which have been observed following its use and practice. This particular chloride has produced results'of outstanding merit under the' preferred conditions of operation, that is elevated 5 rtemperatures of the order of 500 to 650 F., which will be touched upon later, and super-atmospheric pressures high enough to substantially prevent vaporization of th'e oil undergoing treatment.

An important feature of the invention appears in the fact that while treatments are conducted at elevated temperatures that sumcient pressure is held upon the system to maintain the oils in substantially liquid phase. I have determined that when treating cracked distillates that unexpectedly good treating effects in regard to selective removal of gum-forming compounds and sulphur reduction are produced when utilizing temperatures within the approximate range of 500 and 650 F., the pressure required to main- 20 tain cracked distillates containing substantial amounts of gasoline boiling range fractions in liquid phase being of the order of from 400 to 500 lbs., per square inch under these temperature conditions. The exact temperature employed in the treatment will depend upon a number of factors, particularly upon the chemical composition and boiling-range of the naphtha or gasoline undergoing treatment and the physical condition of the zinc chloride, that is its state of subdivision, its moisture content, etc.

The beneficial effects of pressure sufficient to insure substantially liquid phase conditions may be due to several causes. It is probable that the reactions of polymerization and desulfurization proceed with greater velocity in the liquid phase and under increased pressure conditions. At the same time the capacity of treating equipment for permitting a sufilcient time factor is lowered so that the construction of suitable equipment isv less costly than if any appreciable degree of vaporization is permitted. 4

When stabilized distillates are employed which are substantially free from dissolved gases and low boiling hydrocarbons whose critical temperatures may be below the temperatures employed in the treatment. considerably lower pressures may be employed than when unstabilized or poorly stabilized distillates are employed. The curves shown in Fig. 2 indicate the limit conditions of 50 operation which must be adhered to invtreating two gasolines of 114 and 128 mean molecular weight respectively if substantially liquid phase treating conditions are to be maintained.

'Ihe nature of the reactions which have been found to produce the unusually good refining effects upon cracked gasolines when treated according to the process of the invention is diflicult of exact determination on account of the com-` plex character of the hydrocarbon distillates, particularly in regard to the chemical nature of the gum-forming compounds and the form of combination of the sulphur which is present. It may be assumed that the gum-forming compounds consist to a large extentof diand trioleiins of a conjugated character since these compounds are known to readily undergo polymerization. The sulphur compounds may be mercaptans, sulfides, disulfides, thioethers, thiophenes, etc., besides hydrogen sulfide.

The following equations suggest a possible ex-V planation of the course of the reactions of treatment:

It is assumed that hydrochloric acid is the active material in producing reactions of polymerl zation among compounds such as the diand tri-oleiins which are present in cracked distillates, the zinc chloride present functioning catalytically. However, it is possible that the reactions involve some formation of intermediate addition compounds between the zinc chloride and the hydrocarbon radicals. 'I'he determination of the exact course of the reactions of the treatment is beset with great difculties both from the experimental and analytical standpoint. Apparently a very small amont of moisture must be present to insure effective treatment, the necessary quantities being introduced along with the hydrochloric acid. The addition of any excess of water above a certain minimum requirement has been found to be quite uniformly detrimental to the eiiicacy of the treatment.

To account; for the extraordinary ciiiciency oi' the process inremoving sulphur from cracked distillates which are refractory from the standpoint of ordinary sulphuric acid treatments, two types of reactions may be considered, the first involving polymerization of sulphur compoundp' along with the highly unsaturated hydrocarbons so that the sulphur appears in the heavy polymers and, second, those involving a preliminary cornbination of organic sulphur with zinc to form zinc sulde which is later decomposed by hydrochloric acid to evolve hydrogen sulfide as a gas. These reactions are merely assumed and their proof would involve a series of difficult analyses which if not impossible would add little value to the present specification. Some evidence is at hand to show that combined sulphur in high sulphur oils appears after the treatment in mercaptans as a result of secondary reactions of hydrocarbons with hydrogen sulde originally formed. However, with suitable precautions which will be developed in connection with a description of an operation, this tendency toward mercaptan formation can be minimized. The unusual effects along the line of desulfurization will be referred to in the examples which appear later.

Very small amounts of hydrochloric acid are required in the treatments. From the equations given above the hydrochloric acid would be completely regenerated at the end of the polymerizingcycle so that the initial addition of a definite amount of acid would suiiice. However, certain small losses are unavoidable and these are preferably counterbalanced by the addition of the necessary small amounts of acid.

There is apparently some definite relationship between the amount of hydrochloric acid necessary for efficient treatment and the pressure employed upon the system which is shown by the curve in Fig. 3. An inspection of this curve indicates that at the Ypreferred pressures, to wit, 400 to 600 pounds per square inch, that the consumption of hydrochloric acid is reduced to a practical minimum whereas it increases sharply at lower pressures. Aside from the effect of greater concentration of the hydrochloric acid due to the use of higher pressures than have heretofore been employed in similar treating processes, it is possible that the hydrochloric acid 4functions with zinc chloride in a concentrated solution considerably above its maximum solubility in water at ordinary pressures. 'I'he treating effects observed may thus be due to the joint action of hydrochloric acid and zinc chloride in the presence of extremely small amounts of moisture. The small amount of hydrochloric acid necessary for the treatmentmay be added as a substantially dry gas or in concentrated solution.

The process may be conducted in any suitable type of apparatus and Fig. 1 shows diagrammatically by the use of conventional figures in side elevation the essential features of a plant layout which can be used.

Distillates to be treated4 may be introduced to the plant through a line I containing a control valve 2 and pumped by a pump 3 through a line 4 containing control valve 5 into and through a heating element 6 disposed to receive heat from a furnace 'I. After being brought to a suitable temperature for treatment the heated products may be discharged through a line 8 containing a control valve 9 and leading to a line I0. Acid necessary for the treatments may be supplied to a pump I8 through a line I 6 containing a control valve I1 and discharged through a line I9 containing a control valve 20 into line I0 where it mixes with then heated oils. As previously stated the acid may be introduced in a solution of proper concentration to insure the presence of the small amounts of water which are apparently necessary in the treating reactions or may be introduced as a substantially dry gas, the type of pumping equipment represented by number I8 being suitably modified. Y

The acid and oil pass under selected temperature and pressure conditions within the ranges previously mentioned through valve II and enter pressure treater I2 which contains a zinc chloride contact mass I3 dividing the interior of the treater into upper and lower liquid spaces I4 and I5 respectively. During the passage of the oil and acid through the contact mass, degumming and desulfurizing reactions are effected and the products of the treatment pass through line 2I containing control valve 22 to fractionator 23, valve employed may be mixed with or deposited upon relatively inert or adsorbent spacing materials which comprise such substances. as crushed firen Yboiling and substantially unaffected hydrocarbon fractions which may have been present in the raw naphtha if such was treated, and also polymers of olefins. Some sulphur may appear in the polymers in the case of high sulphur stocks and some of the original sulphur may be present in the fractionator in the form of hydrogerf sulfide. It is frequently advantageous in the case of high sulphur oils to utilize pressure treaters in series, the hydrogen sulfide formed in the treating reactions in the first of such a series being vented before further contact is brought about, thus reducing the tendency for metal sulfide formation with corresponding depreciation in the value of the contact material. By venting the fixed gases and thus removing the majority of hydrogen sulfide the formation of mercaptans may be reduced to al practical minimum so that the desulfurization is more effective. Any hydrochloric acid which may be lost when the hydrogen sulfide and other low boiling hydrocarbons or fixed gases are released may be counterbalanced by further additions of acid prior to the succeeding pressure treater. The vented gases may be passed through auxiliary beds of granulated zinc and the chloride and sulfide recovered if desired.

The refluxes from fractionator 23 may be removed through a line. 24 containing a control valve 25 and disposed of in any suitable manner. In case-these reuxes are of fairly low sulphur content and otherwise suitable, they may be used as recycle stock in the cracking plant which may have produced the naphtha or gasoline treated.

The vapors and fixed gases from the fractionator may be conducted through a vapor line 26 containing control valve 21 and be cooled during passage through a condenser 28, the cooled gases and condensed gasoline passing through a rundown line 29 containing control valve 30 to a receiver and separator 3| which has a line 32 containing control valve 33 for the controlled release of fixed gases, a draw line 34 containing control valve 35 for the removal of the finished gasoline and a bottom draw line 36 containing control valve 31 for removal of water or aqueous solution which may accumulate in the receiver.

The field of application of the process is extensive and the examples of the results obtainable up'on different stocks could be multiplied to a considerable extent. A few, however, will suffice to show the advantages of the process over the more commonly used systems of treatment.

An untreated cracked gasoline made from a relatively high sulphur Texas charging oil may be treated in equipment generally similar to that shown in Fig. l at a temperature of 560 F. and a pressure o'f 450 pounds per square inch. The contact mass employed in the pressure treater may consist of zince chloride mixed with three parts by weight of pumice and hydrochloric acid may be admitted to the treating zone at a rate corresponding to 0.15 pound per barrel of nished gasoline, the small amount passing out of the treating zone being absorbed during passage of the treated oils and fixed gases through auxiliary beds of granulated zinc. The following table shows the relative properties of the raw or untreated gasoline and-the properties of the finished 5 gasoline, the properties ofthe latter being determined after the passage of approximately 8000 barrels of gasoline through 1' ton of. contact materials.

Comparsz'on of raw and treatedgctsolines.v .lo

Treated Alter 4 hrs. exposure to sunlight.

Comparison of raw and treated gasolines Color. Color stability* Mg. of gum/100 cc. y copper d Octane number A 67 Induction period in oxygen bomb-minutes: 40

*After i hrs. exposure to sunlight.

N The results obtained by the process as evidenced by 'the two preceding examples are striking from several standpoints. It will be observed that in both cases the color and color stability were betterthan those obtainable even by the use of commercially prohibitive amounts of sulphuric acidas shown in other experiments. The gum content was reduced to a figure below that required in premium gasolines and the odor was perfectly sweet. In the first example the sulphur reduction is especially noteworthy since Texas pressure distillates are notoriously refractory in regard to desulfurization by sulfuric acid or other methods of treatment.

The treating losses suffered were approximately 2% in both cases and this fact coupled with the extremely high quality of the treated product is of itself sufficient to recommend the process for the treatment'of cracked gasoline of any character. The selectivity of the treatment in regard to the removal of gum-forming olens without affecting mono-olefins is evident from the second example in the maintenance of the octane number after treatment while the oxygen bomb test which generally indicates the stability of the gasoline on storage is/raised to a point considerably in excess of the minimum of 240 minutes which is at present accepted as indicating a gasoline sufficiently' stable under average storage conditions.

The foregoing disclosure of the nature of the invention and the numerical data presented in support of its commercial value are sufllcient forl comprises treating the oil with added aqueous hydrogen chloride in the presence of a solid contact agent comprising zinc chloride at a temperature substantially above the normal initial boiling point of the oil while under sulcient super-atmospheric pressure to maintain the 011 substantially in liquid phase.

3. A process for refining gasoline-containing distillates which comprises treating the distillate with added aqueous hydrogen chloride in the presence of added zinc chloride at a temperature of from 500 F. to 650 F. and under a pressure of at least 400 pounds per square inch.

ROLAND B. DAY. 

